public async Task GetMetricsAsync()
{
var r = Metric.NewCustomRegistry();
MetricFactory f = Metric.WithCustomRegistry(r);
r.AddBeforeCollectCallback(() =>
{
f.CreateCounter("counter_v1", "").Inc(100);
});
Response.ContentType = PrometheusConstants.ExporterContentType;
Response.StatusCode = 200;
await r.CollectAndExportAsTextAsync(Response.Body, HttpContext.RequestAborted);
}